Patent Application
20110127043
The invention generally relates to a gas lift valve.
A well typically includes a production tubing string for purposes of communicating well fluid to a surface of the well through a central passageway of the string. Due to its weight, the column of well fluid that is present in the production tubing string may suppress the rate at which the well fluid is produced from the formation. More specifically, the column of well fluid inside the production tubing string exerts a hydrostatic pressure that increases with well depth. Near a particular producing formation, the hydrostatic pressure may be significant enough to substantially impede the rate at which the well fluid is produced.
For purposes of reducing the hydrostatic pressure and thus, enhancing the rate at which fluid is produced, an artificial-lift technique may be employed. One such technique involves at various downhole points in the well, injecting gas into the central passageway of the production tubing string to lift the well fluid in the string. The injected gas, which is lighter than the well fluid displaces some amount of well fluid in the string. The displacement of the well fluid with the lighter gas reduces the hydrostatic pressure inside the production tubing string and allows the reservoir fluid to enter the wellbore at a higher flow rate. The gas to be injected into the production tubing string typically is conveyed downhole via the annulus (the annular space surrounding the string) and enters the string through one or more gas lift valves.
In one example, a gas lift valve assembly includes a housing that includes a first passageway that is substantially concentric with the central passageway of a string to communicate well fluid and a second passageway that is eccentrically disposed with respect to the central passageway to communicate a second fluid to lift the well fluid. The gas lift valve assembly includes a valve that is disposed in the second passageway and includes a ball valve to regulate communication of the second fluid.
In another example, a method includes providing a gas lift valve that includes a ball valve element and operating the ball valve element to regulate fluid communication through the gas lift valve.
In yet another example, a system includes a string that includes a central passageway to communicate well fluid to the surface and gas lift valve assemblies. At least one of the gas lift valve assemblies includes a ball valve to regulate communication of a gas lift fluid into the central passageway of the string.
Advantages and other features of the invention will become apparent from the following drawing, description and claims.
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments are possible.
As used here, the terms “above” and “below”; “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or diagonal relationship as appropriate.
Referring to
As depicted in
More specifically, as an example, the production tubing string 14 may include several side pocket gas lift mandrels 16 (gas lift mandrels 16a, 16b and 16c, being depicted as examples in
As described herein, the gas lift valves 18 are injection pressure operated (IPO) valves. In general, an IPO valve opens when the annulus pressure exceeds the production tubing string pressure by a certain threshold. The pressure thresholds of the gas lift valves 18 may be separately configured, which permits the gas lift valves 18 to be opened in a certain sequence. It is noted that the production tubing string 18 may contain more or less than the three gas lift valves 18 that are depicted in
As described herein, the gas lift valve 18 includes a ball valve 19, which is constructed to be operated such that when the pressure of the annulus 15 near the gas lift valve 18 exceeds a certain threshold, the ball valve 19 opens to permit communication between the surrounding annulus and the central passageway of the production tubing string 14. The ball valve 19 is further constructed to automatically close when the annulus pressure near the gas lift valve 18 decreases below the threshold.
Due to the use of the ball valve 19 to control the flow through the valve 18, the valve 18 may be used in a barrier application. As a comparison, a conventional gas lift valve may use a check dart-type valve element for purposes of preventing a reverse flow through the gas lift valve when closed. However, these valve elements may deform when the element is used over a relatively wide pressure range, and this deformation may cause leakage. As such, conventional gas lift valves may not be suitable for a barrier application, which needs to seal over a wide range of pressures. In contrast, the ball valve design is capable of sealing over a wide range of pressures and thus, is suitable for use as a barrier device.
Referring to
As shown in
In general, the gas lift valve 18 controls fluid communication between the annulus 15 and the central passageway of the production tubing string 14 in the following manner. As long as the annulus pressure is below a certain threshold, the ball valve 19 of the gas lift valve 18 remains closed to block fluid communication between the inlet port(s) 58 and an outlet port 52 of the gas lift valve 18. Thus, when the ball valve 19 is closed, fluid communication does not occur through the gas lift valve 18. When the annulus pressure exceeds the threshold, as described further below, the ball valve 19 opens to permit fluid communication between the inlet port(s) 58 and the outlet port 52. When the ball valve 19 is open, fluid thus is communicated between the annulus 15, into the inlet port(s) 58, through the ball valve 19, through the outlet port 52, through the port(s) 36 and into the central passageway of the production tubing string 14.
It is noted that the gas lift valve 18 may be installed and/or removed from the production tubing string 14 by a wireline operation (as a non-limiting example). In this regard, as a non-limiting example, the gas lift valve 18 may include a latch 62, which is engageable by a tool at the end of a wireline for purposes of securing the gas lift valve 18 inside the passageway 32, as well as releasing the gas lift valve 18 from the side pocket mandrel 16 for purposes of retrieving the valve 18 to the surface of the well 10.
Referring to
Referring to
The ball element 100 includes a central passageway 104, which is aligned with the central passageway of the production tubing string 14 in the open state of the ball valve 19. In the closed state of the ball valve 19, the ball element 100 is rotated so that the passageway 104 is no longer aligned with the central passageway of the production tubing string 14, but rather, for this orientation of the element 100, the solid portion of the element 100 blocks fluid communication through the valve 19.
The angular orientation of the ball element 100 about the axis 102 is controlled by a yoke 106 and a pin 110. The pin 110 is located near a lower end of the yoke 106 and resides in a slot 105 of the ball element 100. In general, the free end of the pin 110 resides in a longitudinal slot inside the housing of the gas lift valve 18 and is confined by the slot to move along the longitudinal axis 120 with the longitudinal translation of the yoke 106. Due to the eccentric positioning of the pin 110 with respect to the axis 102 of the ball element 100, upward movement of the yoke 106 causes the ball element 100 to rotate about the axis 102 to its closed position. Conversely, downward travel of the yoke 106 causes an opposite rotation of the ball element 100 for purposes of returning the ball element 100 to its open position (as depicted in
The well fluid that enters the radial ports 58 exerts a pressure on a lower surface of the bellows 150 to form a corresponding upward force on the bellows 150. This upward force, in turn, is countered by a downward force that is created by a stored gas charge. The bellows 150 is connected to the operator 112 of the yoke 106 so that upward and downward movement of the bellows 150 induces a corresponding longitudinal translation of the yoke 106 and thus, controls the open and closed state of the ball valve 19.
A force that is created by gas in a pressurized upper gas chamber 160 of the gas lift valve 18 exerts a downward force on the opposite side of the bellows 150. In general, the gas pressure inside the chamber 160 biases the yoke 106 downwardly, thereby biasing the ball valve 19 to rotate to a position to form a fluid blocking seal against a valve seat 177 to close the valve 19. This biasing force, in turn, is overcome when the pressure that is exerted by the annulus fluid exceeds a predefined threshold. When this occurs, the upward force on the bellows 150 exceeds the downward force exerted by the gas in the chamber 160 to cause upward movement of the bellows 150 and yoke 106, thereby transitioning the ball valve 19 to its open state and permitting fluid communication through the ball valve seat 177 and port 52.
The annulus pressure required to open the ball valve 19 is set by the pressure charge inside the chamber 160. As depicted in
In general, when the ball valve 19 is open, fluid is communicated between the inlet ports 58 and the outlet port 52 of the gas lift valve. As depicted in
In accordance with a non-limiting example, the gas lift valve 18 may include energized seal assemblies 200 (T-seal assemblies, V-seal assemblies, chevron assemblies, o-ring assemblies, etc.) to seal the ball element 110 against the ball valve seat 177. The energized seal assemblies 200 relax the tolerance requirements for the ball valve 19 and permit ease of operating the ball valve 19, especially in the case of high annulus pressures.
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
